Heretofore, various UV absorbers such as the benzophenones, benzotriazoles and resorcinol monobenzoates have been incorporated into polymers as discussed in Plastics Additives Handbook, Hanser Publishers, Library of Congress Catalog No. 83-062289, pp 128-134, for use in absorbing or screening deleterious radiation. These additives function well to screen radiation in the range of from about 300 to about 350 nm; however, this range is not adequate to protect the contents of food packaging employing these polymers. Moreover, when these compounds are added to polyesters, they are extractable by solvents which may be present in food packaged with the polymers. Such solvents would include typical food acids, alcohols and the like. Furthermore, these compounds are not, in general, stable under the polyester manufacturing and processing conditions and often produce objectionable yellow discoloration in food packaging. Also, the various copolyesters such as disclosed in U.S. Pat. No. 4,338,247, while having essentially nonextractable UV absorbers, are not suitable for food packaging in that the absorbers transmit harmful radiation and are not designed to protect food.
U.S. Pat. No. 3,634,320 discloses compounds somewhat similar to those disclosed herein for mixing into various polymers for U.V. absorption, however, copolymerization is not involved and the wavelength of maximum absorption for these compounds are not sufficiently high to protect food.